1 files changed, 52 insertions, 9 deletions

diff --git a/libs/timecode/timecode/bbt_time.h b/libs/timecode/timecode/bbt_time.h
index b3ba3a6b57..b42ccf741e 100644
--- a/libs/timecode/timecode/bbt_time.h
+++ b/libs/timecode/timecode/bbt_time.h
@@ -22,26 +22,31 @@
 #include <ostream>
 #include <stdint.h>
 #include <iomanip>
+#include <exception>
 
 #include "timecode/visibility.h"
 
 namespace Timecode {
 
 /** Bar, Beat, Tick Time (i.e. Tempo-Based Time) */
-struct LIBTIMECODE_API BBT_Time {
+struct LIBTIMECODE_API BBT_Time
+{
 	static const double ticks_per_beat;
 
-	uint32_t bars;
-	uint32_t beats;
-	uint32_t ticks;
+	/* note that it is illegal for BBT_Time to have bars==0 or
+	 * beats==0. The "neutral" or "default" value is 1|1|0
+	 */
 
-	BBT_Time ()
-		: bars (1), beats (1), ticks (0) {}
+	int32_t bars;
+	int32_t beats;
+	int32_t ticks;
 
-	BBT_Time (uint32_t ba, uint32_t be, uint32_t t)
-		: bars (ba), beats (be), ticks (t) {}
+	struct IllegalBBTTimeException : public std::exception {
+		virtual const char* what() const throw() { return "illegal BBT time (bars or beats were zero)"; }
+	};
 
-	BBT_Time (double beats);
+	BBT_Time () : bars (1), beats (1), ticks (0) {}
+	BBT_Time (int32_t ba, uint32_t be, uint32_t t) : bars (ba), beats (be), ticks (t) { if (!bars || !beats) { throw IllegalBBTTimeException(); } }
 
 	bool operator< (const BBT_Time& other) const {
 		return bars < other.bars ||
@@ -74,6 +79,37 @@ struct LIBTIMECODE_API BBT_Time {
 	bool operator!= (const BBT_Time& other) const {
 		return bars != other.bars || beats != other.beats || ticks != other.ticks;
 	}
+
+	/* it would be nice to provide operator+(BBT_Time const&) and
+	 * operator-(BBT_Time const&) but this math requires knowledge of the
+	 * meter (time signature) used to define 1 bar, and so cannot be
+	 * carried out with only two BBT_Time values.
+	 */
+
+	BBT_Time round_to_beat () const { return ticks >= (ticks_per_beat/2) ? BBT_Time (bars, beats+1, 0) : BBT_Time (bars, beats, 0); }
+	BBT_Time round_down_to_beat () const { return BBT_Time (bars, beats, 0); }
+	BBT_Time round_up_to_beat () const { return ticks ? BBT_Time (bars, beats+1, 0) : *this; }
+
+	/* cannot implement round_to_bar() without knowing meter (time
+	 * signature) information.
+	 */
+};
+
+struct LIBTIMECODE_API BBT_Offset
+{
+	int32_t bars;
+	int32_t beats;
+	int32_t ticks;
+
+	/* this is a variant for which bars==0 and/or beats==0 is legal. It
+	 * represents an offset from a given BBT_Time and is used when doing
+	 * add/subtract operations on a BBT_Time.
+	 */
+
+	BBT_Offset () : bars (0), beats (0), ticks (0) {}
+	BBT_Offset (int32_t ba, uint32_t be, uint32_t t) : bars (ba), beats (be), ticks (t) {}
+	BBT_Offset (BBT_Time const & bbt) : bars (bbt.bars), beats (bbt.beats), ticks (bbt.ticks) {}
+	BBT_Offset (double beats);
 };
 
 }
@@ -86,6 +122,13 @@ operator<< (std::ostream& o, const Timecode::BBT_Time& bbt)
 }
 
 inline std::ostream&
+operator<< (std::ostream& o, const Timecode::BBT_Offset& bbt)
+{
+	o << bbt.bars << '|' << bbt.beats << '|' << bbt.ticks;
+	return o;
+}
+
+inline std::ostream&
 print_padded (std::ostream& o, const Timecode::BBT_Time& bbt)
 {
 	o << std::setfill ('0') << std::right